#include<bits/stdc++.h> using namespace std; int n,m,k,x,y; float f[1001][1001]={0}; bool a[1001][1001]={0}; int main() { cin>>n>>m; cin>>k; for(int i=0;i<k;i++) { cin>>x>>y; a[x+1][y+1]=1; } for(int i=1;i<=n+1;i++) { for(int j=1;j<=m+1;j++) { if(i>1&&j>1) f[i][j]=100+min(f[i-1][j],f[i][j-1]); if(i==1&&j>1) { if(f[i][j]==0) f[i][j]=100+f[i][j-1]; else f[i][j]=100+min(f[i][j],f[i][j-1]); } if(i>1&&j==1) { if(f[i][j]==0) f[i][j]=100+f[i-1][j]; else f[i][j]=100+min(f[i][j],f[i-1][j]); } if(a[i][j]==1&&f[i][j]>(f[i-1][j-1]+sqrt(20000))) f[i][j]=f[i-1][j-1]+sqrt(20000); } } cout<<(int)(f[n+1][m+1]+0.5)<<endl; return 0; }